Apparatus for determining and marking focal center of spherical lenses.



I,2I7. Patented Ian. l4, I902; No 69 J. WEST. APPARATUS FOR DETERMINING AND MARKING FOCAL CENTER OF SPHERIGAL LENSES.

(Application filed Kay 20, 1901.1

3 Sheets-Sheet I.

(No Model.)

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No. 691,2l7.

(No Mod el.)

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No. 69I,2I7. Patented Ian. I4, I902.

' J. WEST. APPARATUS FOR DETERMINING AND MARKING FOCAL CENTER OF SPHERICAL LENSES.

(Application filed May 20. 1901. (No Model.) 3 Sheets-Sheet 3.

UNITE reins JAMES VEST, OF DALSTON, ENGLAND, ASSIGNOR OF T WO-THIRDS TO HENRY JOSEPH \VILBERFOROE RAPHAEL, OF SHEPHERDS BUSI-I, MIDDLESEX COUNTY, ENGLAND, AND HERMANN LIONEL ETIINGHAUSEN, OE" LON- DON, ENGLAND.

APPARATUS FOR DETERMINING AND MARKING FOCAL CENTER OF SPHERICAL LENSES.

SPECIFIGATION forming part of Letters Patent No. 691,217, dated. January 14;, 1902. Application filed May 20,1901. Serial No, 61,135. (No model.)

To all 1071,0722, it may concern:

Be it known that I, JAMES VEST, a subject of the King of Great Britain, residing at Dalston, in the county of Middlesex, England,

have invented a certain new and useful Improvementin Apparatus for Determining and Marking the Focal Center of Spherical Lenses, of which the following is a specification.

My invention relates to improvements in apparatus for determining and marking the focal center of sphericallenses; and the object of my improvement is, first, to determine very rapidly and accurately the exact focal center of the lens, and, second, to mark upon the lens the exact position of the focal center when determined. I attain these objects by the means illustrated in the accompanying drawings, in which- Figure 1 is a sectional view of the entire apparatus. Fig. 2 shows Vertical and horizontal sections through the parts of the apparatus. Fig. 3 is a front view of the same. Fig. 4 is a plan of the same.

Similar letters refer to similar parts through- 2 5 out the several views.

The improved apparatus for ascertaining the focal center of spherical lenses consists, primarily, of two pieces of cylindrical tubing accurately turned and faced and held in guides arranged one above the other, which carry them closely andaccurately into alinement with each other. The upper one of these two tubes is capable of a sliding movement in the direction of its length and can be moved by hand by means of a knob. This upper tube is arranged to descend upon the lower tube, so that the two stand upon end, one accurately over the other, without showing any joint.

(1 is the upper piece of cylindrical tubing, which can be raised or lowered in the guide 01 by means of the milled knob or handle 0.

b is the lower piece of cylindrical tubing, supported in the bored guide or socket e and 5 lying in perfect alinement with the upper piece a, so that when-the latter is brought down it accurately meets the lower one without showing any joint.

The guides 01 and e are arranged in a suitably-shaped standard shown rising'out of a tripod base at fin Figs. 1, 3, and l.

The lens to be centered after raising the upper tube to admit it is laid flatwise upon the mouth of the lower tube 1), and the upper tube a is then brought down to bear upon the upper face of the lens, and so clamp it between the ends of the two tubes. At this stage the operator takes the lens by its overhanging edges between his thumb and finger, giving it a slight sliding movement until he.6o finds that the lens snugly beds between the ends of the opposing tubes.

It will be seen that the greater the convexity and concavity of the lenses the more easily and readily the lens can be centered, while the more the lens approximates to flatness the more careful and dexterous the operator must be.

The ends of the tubes a and b may be coated with a facing of suitable material to prevent the lens from being scratched.

In Fig. 2, g shows the lens in the position of being centered,-as just described.

It is sometimes necessary to mark the focal center of a lens, and for this purpose the improved apparatus is provided with a marking device, (shown in Fig. 2,) in which his a cylinder or drum fitting centrally in the tube a and moving with it. 11 is a pencil or pen sliding in the ends of the drum 7t and operated by a milled knob j, while it is kept up to a stop by the spring It. In the position shown it will be seen that when the point of the pencil 2' is made to descend upon the lens 9 the point marked thereon will be the true focal center.

It is sometimes necessary to remove the lens from the position shown in Fig. 2 by means of tongs taking hold of it byits center and of the kind fully set forth and claimed in my concurrent application, Serial No. 61,136, filed May 20, 1901. For this purpose an orifice is formed in the tubes a and I) to admit the nose of such tongs or equivalent device. Such an orifice is shown at Zin Figs.

1 and 3. The orifice is formed partly in the 5 upper and partly in the lower tube, so that when the two are brought together it is complete, as shown in Figs. 1 and 3.

It is sometimes advisable to adjust the height of the top edge or mouth of the lower tube 2') to a given point above the base, and for this purpose the apparatus is provided with a micrometer-screw adjustment, (shown in Figs. 1, 3, and 4,) in which at is a screw having a fine thread and provided with a collar 11, resting in a shouldered recess and secured by a separate collar 0, the lower end of the screw terminating in a long indicator-hand h, moving over a dial q, while its upper end controllably moves the lower tube b'upward or downward, as may be required.

Having fully described my invention, What I desire to claim and secure by Letters Patent 1s 1. In a device of the character described the combination with a stand having tubular guides in line with each other, a tube mounted in one of said guides and means for adjusting the height of said tube with relation to the said stand; of a tube mounted to slide in the other guide, the said tubes having their adjacent ends open and accurately faced at right angles to their center lines, and a pointed plunger mounted to slide centrally in one of the said tubes; substantially as described.

2. In a device of the character described the combination with a stand having tubular guides in line with each other, a tube mounted in one of said guides and means for adjusting the height of said tube with relation to the said stand; of a tube mounted to slide in the other guide, the said tubes having their adjacent ends open and accurately faced at right angles to their center lines, a pointed plunger mounted to slide centrally in one of the said tubes, and a spring tending to hold said plunger away from the meeting end of the said tubes, substantially as described.

3. In a device of the character described the combination with a stand having tubular guides in line with each other, a tube mounted in one of said guides and means for adjusting the height of said tube with relation to the said stand; of a tube mounted to slide in the other guide, the said. tubes having their adjacent ends open and accurately faced at right angles to their center lines, and having openings Z in one side thereof, a pointed plunger mounted to slide centrally in one of the said tubes, and means for holding the said plunger away from the meeting ends of the said tubes; substantially as described.

In Witness whereof I have hereunto set my hand in the presence of two Witnesses.

JAMES WEST.

Witnesses:

ALFRED G. BRATTON, I-L ARTHUR MARsHALL. 

